Installer

- Fix entry point handling in {any}`installer.install`.

- Teach {any}`SchemeDictionaryDestination` to create subfolders.

- Change {any}`parse_record_file` to yield the elements as a tuple, instead of
{any}`RecordEntry` objects.
- Implement {any}`WheelFile`, completing the end-to-end wheel installation
pipeline.
- Generate {any}`RecordEntry` for `RECORD` file in the {any}`installer.install`,
instead of requiring every `WheelDestination` implementation to do the exact
same thing.

- Initial release.

---

Thank you to [Dan Ryan] and [Tzu-ping Chung] for the project name on PyPI. The
PyPI releases before 0.2.0 come from <https://github.com/sarugaku/installer> and
have been [yanked].

[dan ryan]: https://github.com/techalchemy
[tzu-ping chung]: https://github.com/uranusjr
[yanked]: https://www.python.org/dev/peps/pep-0592/#abstract